Engine Coolant Temperature Sensor: Operation

The engine coolant temperature sensor provides an input to the powertrain control module (PCM). As coolant temperature varies, the engine coolant temperature sensor resistance changes, resulting in a variable input voltage to the PCM.

When the engine is cold, the PCM will demand slightly richer air-fuel mixtures and higher idle speeds until normal operating temperatures are reached.

The engine coolant sensor input also determines operation of the radiator fan.